log.exception does not work when there is no exception

[evandrocoan]

It outputs:

Traceback (most recent call last):
  File "./python3.3/logging/__init__.py", line 939, in emit
  File "./python3.3/logging/__init__.py", line 810, in format
  File "./python3.3/logging/__init__.py", line 556, in format
  File "./python3.3/logging/__init__.py", line 506, in formatException
  File "./python3.3/traceback.py", line 156, in print_exception
  File "./python3.3/traceback.py", line 122, in _iter_chain
AttributeError: 'NoneType' object has no attribute '__context__'
Logged from file third_part.py, line 176

For the input:

def load_data_file(file_path, wait_on_error=True, log_level=1, exceptions=False):
    channel_dictionary = OrderedDict()

    if os.path.exists( file_path ):
        maximum_attempts = 10

        while maximum_attempts > 0:

            try:
                with open( file_path, 'r', encoding='utf-8' ) as data_file:
                    return json.load( data_file, object_pairs_hook=OrderedDict )

            except ValueError as error:
                log( 1, "maximum_attempts %d, %s (%s)" % ( maximum_attempts, error, file_path ) )
                maximum_attempts -= 1

                if wait_on_error:
                    time.sleep( 0.1 )

        if maximum_attempts < 1:
            log.exception( "Could not open the file_path: %s" % ( file_path ) )
            if exceptions: raise